The detection of a signal of interest and the discernment of noise and its constituency have always been of high interest to those who must assure reliable communications. These considerations are foremost in the minds of operators of very low frequency (VLF) systems since systems of this type have been selected to convey information that is most important. Any delays in recognizing information and various interferences could have severe consequences. So the need continues for an apparatus for visually aiding a rapid analysis of incoming signals, such as VLF, and, more particularly, the detection, interference recognition and classification of minimum shift keying (MSK) signals in incoming VLF signals.
A VLF receiving terminal operator sitting at a console must determine the nature and electromagnetic noise environment of the incoming signal usually without any previous knowledge about the signal. One prior art approach relies upon the use of trained operators who listen to audio outputs and develop an "ear" for judging the incoming signal traffic. A main drawback of this approach is that its success is contingent solely upon the level of operator skill which inherently varies from one individual to the next. Furthermore, the audio monitoring of signals for a period of time can be tedious and fatigue may set in to compromise performance.
Another prior art approach to improve performance is to give an operator a visual indication by employing a spectrum analyzer to "see" the frequency characteristic of the environment. Drawbacks of this approach are that it has relatively slow response and requires considerable expensive equipment.
In view of the aforementioned drawbacks of these prior art approaches, a continuing need exists in the state of the art for a cost effective visual monitoring of a signal of interest to aid a receiving terminal operator in the task of identifying signals of interest and of determining the nature and noise environment of incoming signals.